The present invention relates generally to a self-aligning grip housing and load train column assembly by which a uniaxial load can be transmitted through the centerline of a ceramic tensile specimen without introducing bending stresses.
Recent developments in ceramic materials have substantially advanced the state of the art and have resulted in the development of interest in such materials for use in heat engines and high-temperature conversion systems such as gas turbines.
Because the fractural strength of structural ceramics is vitally important to their use as engineering structural materials, means for accurately testing the tensile strength of ceramic specimens are needed to evaluate and characterize newly developed ceramic materials. Tensile testing of ceramics is inherently difficult due to the concentric load transfer (the avoidance of bending stresses in the specimen) being very critical to the accuracy of the test results.
Limited success in concentric load transfer to ceramic specimens during tensil testing has been achieved through the use of universal joints or equivalent mechanisms to avoid the occurrence of specimen bending from the loading mechanism. A set of lubricated hemispherical bearings has been used in the load train for ceramic tensile measurements in an attempt to eliminate all bending moments in the test specimen. The use of flexible cable to transmit loads has also provided a degree of success. There remains however a need for a simple economical procedure for measuring tensile cyclic fatigue properties of ceramics with little or no bending stresses being transmitted to the ceramic specimen during testing.
It is accordingly a general object of this invention to provide means for accurately testing the tensil strength of ceramic specimens. Another, more particular object of the invention is to provide a means for loading a ceramic specimen during a tensile test with little or no bending stresses being transmitted to the specimen.